The last decade has seen tremendous developments in gamma-ray astronomy
with the extragalactic sky becoming highly populated by Active Galactic Nuclei (AGNs).
This brief review highlights some of the progress in AGN research achieved over the
years, and discusses exemplary advances in the theory and physics of gamma-ray loud
AGNs, including black-hole magnetospheric processes, the physics of pc-scales jets, as
well as particle acceleration and high-energy emission in the large-scale jets of AGNs.